Is the 4wd Computer accessable on Techstream?
- Thread starter Miranthis
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What part exactly? There is no "4wd ECU" on any 4runner. There is the ABS computer which has the ATRAC integrated into it and the Engine computer or ECU. What parameter are you trying to view?
Just did not see a data line in any of there streams for the 4wd being engaged in 4H or 4LO or the "differential lock" being engaged or not. I understood from the various threads that there was a 4wd 'computer' on the passenger side near the kick panel that electronically controlled the transfer case and front differential actuation, taking input from the switch on the dash.
I have been exploring the available data and various customization settings and realized all the systems except the 4wd had a pretty obvious home ECU to look at, even if there was no customization available.
unevolved
Member
I believe that computer, as well as the rear locker computer, are all analog. Just look at limit switch statuses and make a decision on what to do next. I don't recall seeing any serial communication lines when helping a friend diagnose a faulty 4WD system.
damthemainstream
New member
What's this then?
Well "computer" in the sense that it is written on the sticker, and that is the limit of its computing power. I can guarantee that it does not appear in Techstream as the "4WD computer", in fact I was just using Techstream yesterday and did not see it.
damthemainstream
New member
What the hell does it do though?
This was exactly my question. There are a number of ECU/ECMs on the 08 4Runner, not nearly as many as my 12 Camry but still a lot. Most of those, if not all, appear to fail your definition of "computer", but yet are just a bunch of ICs and chips that produce output from input. The integration control module on my 01 sienna also is such a collection, but not "on the bus" or accessible as an module on Techstream.
I just wondered as I found data streams for AT electronic control actions and wondered whether the electronic 4WD controls were similarly represented. If I understand the CAN bus standard correctly, eventually all the control nodes of modern vehicles will be accessible on OBDII software, or at least that is one goal.
It reads the position of the 4wd dash switch and the various position sensors in the transfer case/AT/differentials and governs the actuation of the motors/servos that make the shifts between 2H, 4H, and 4L. It requires things being done in a certain order (motors and rods etc.) and it uses self diagnosis to govern those lights on the dash to tell us if it is done, or still working.
Basically, its the 'black box' that makes the right lights go on and off, and the right gears and such to engage/disengage.
BlackWorksInc
New member
It's a module that has a very specific functionality, it is not connected to the CAN Bus and has no self-diagnostic capability (i.e. no DTC storage or Data List, ect.) This is not uncommon on vehicles, some modules/computers are very simple and don't connect to the vehicle's network, others do connect but have limited functionality through other modules, ect. There's a lot more computers/modules in a vehicle and not all of them are set-up like say an ECM, ABS, or SRS Module that communicates on the CAN Bus/Multiplex networks, sometimes they're just modules that exist in their own ecosystem doing what they do.
For example on newer vehicles with multiple Auto Up/Down windows, the individual window switches are actually modules and they communicate on an enclosed data bus through the main body module (which acts as a gateway/router), but on a system check you'll maybe see a Master Switch show up (though more often than not you won't and any data/diagnostics is accessed through the Main Body Module). Another example of this is the Back Door ECU on 4th gens, it controls all the functions of the back door; but it does not have a connection to the CAN Bus and is not accessible from the techstream, though some data can be pulled from the Main Body ECU if I recall.
Newer Toyotas made in the last couple years have DTCs and some limited diagnostic features and do respond on the CAN Bus but it's not much more than what your 4th gen's 4WD module does already.
For example on newer vehicles with multiple Auto Up/Down windows, the individual window switches are actually modules and they communicate on an enclosed data bus through the main body module (which acts as a gateway/router), but on a system check you'll maybe see a Master Switch show up (though more often than not you won't and any data/diagnostics is accessed through the Main Body Module). Another example of this is the Back Door ECU on 4th gens, it controls all the functions of the back door; but it does not have a connection to the CAN Bus and is not accessible from the techstream, though some data can be pulled from the Main Body ECU if I recall.
Newer Toyotas made in the last couple years have DTCs and some limited diagnostic features and do respond on the CAN Bus but it's not much more than what your 4th gen's 4WD module does already.
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